Surveillance of Invasive Bacterial Disease in Alaska, 2016 

Arctic Investigations Program 

National Center for Emerging & Zoonotic Infectious Diseases 

Centers for Disease Control and Prevention 

4055 Tudor Centre Dr. 

Anchorage, AK 99508 

(907) 729-3400 

ncidaip@cdc.gov
Surveillance of Invasive Bacterial Disease in Alaska, 2016 2
Surveillance of Invasive Bacterial Disease in Alaska, 2016 3

Alaska Statewide Invasive Bacterial Disease 

Table of Contents 

 Page 

Summary 4 

Introduction 5 

Invasive Pneumococcal Disease 6 

Invasive Haemophilus influenzae 15 

 

Invasive Neisseria meningitidis 19 

Invasive Group A Streptococcus 20 

Invasive Group B Streptococcus 21 

References 28 

Appendix 29 
Surveillance of Invasive Bacterial Disease in Alaska, 2016 4

Summary 

The Centers for Disease Control and Prevention's Arctic Investigations Program (AIP) in Anchorage, Alaska, 

maintains a statewide surveillance system for invasive diseases caused by Streptococcus pneumoniae, 

Haemophilus influenzae, Neisseria meningitidis, and groups A and B streptococci. Laboratories throughout the 

state are requested to send to AIP any isolates of these organisms recovered from blood, CSF, or other normally 

sterile site in an Alaska resident. Isolate identification is confirmed and, when appropriate, isolates are 

serotyped/serogrouped and tested for antimicrobial susceptibility. The objectives of this system are to provide 

information on disease rates within the state, monitor the emergence of antimicrobial resistance, and to monitor 

the effectiveness of implemented vaccine programs, such as the 23-valent pneumococcal polysaccharide 

vaccine, the pneumococcal conjugate vaccine and Haemophilus influenzae type b vaccines. 

Figure 1: Invasive Bacterial Disease Surveillance Regions – Alaska, 2016 

In 2016, the total numbers of cases of invasive disease caused by these organisms reported to AIP were 131 S. 

pneumoniae, 19 H. influenzae, 7 N. meningitidis, 145 group A Streptococcus (GAS) and 68 group B 

Streptococci (GBS). Alaska Native people had higher rates of disease overall than non-Native people for all 

surveillance organisms. Rates of invasive pneumococcal disease were highest in the YK Delta and Kotzebue 

regions. Rates for each organism by region are presented in the following table. 

Arctic Slope 

Interior 

Kotzebue 

Norton Sound 

YK Delta 

Bristol Bay 

Anchorage 

Southeast 
Surveillance of Invasive Bacterial Disease in Alaska, 2016 5

Table 1: Surveillance Organisms Reported by Region – Alaska, 2016 

Region 

S. pneumoniae 

n (rate*) 

H. influenzae 

n (rate*) 

N. meningitidis 

n (rate*) 

GAS 

n (rate*) 

GBS 

n (rate*) 

Anchorage 86 (17.5) 10 (2) 2 (0.4) 100 (20.3) 50 (10.2) 

Arctic Slope 0 (0) 0 (0) 0 (0) 2 (22.8) 0 (0) 

Bristol Bay 0 (0) 1 (14.1) 0 (0) 1 (14.1) 0 (0) 

Interior 20 (17.8) 0 (0) 0 (0) 15 (13.4) 11 (9.8) 

Kotzebue 2 (23.2) 0 (0) 2 (23.2) 4 (46.4) 1 (11.6) 

Norton Sound 2 (19.8) 1 (9.9) 0 (0) 1 (9.9) 1 (9.9)

Southeast 9 (12.2) 2 (2.7) 1 (1.4) 3 (4.1) 5 (6.8) 

YK Delta 12 (45.3) 5 (18.9) 2 (7.5) 19 (71.7) 0 (0)

Total 131 (17.7) 19 (2.6) 7 (1.0) 145 (19.6) 68 (9.2) 

*Cases per 100,000 population 

Introduction 

AIP conducts statewide surveillance of invasive Streptococcus pneumoniae, Haemophilus influenzae, Neisseria 

meningitidis, and groups A and B Streptococcus. This program is part of a passive, laboratory-based 

surveillance system in which laboratories from all hospitals throughout the state are encouraged to participate. 

The population included in the AIP surveillance is the State of Alaska, which totaled 739,828 persons in 2016 

[1]. Case detection occurs year-round as participating laboratories send isolates recovered from sterile sites to 

the AIP laboratory in Anchorage; materials and forms for isolate shipment and data collection are provided to 

each laboratory by AIP. Demographic and clinical information on the cases are collected from a review of 

medical records. At year-end, AIP asks that each laboratory review their records and provide information on 

any cases that may have been overlooked. In 2016, 22 laboratories in Alaska participated in the invasive 

disease surveillance system, either by sending isolates to the AIP laboratory throughout the year, conducting 

year-end record reviews, or both. Invasive S. pneumoniae, H. influenzae, N. meningitidis, GAS and GBS are 

reportable conditions to the State of Alaska Division of Public Health (DPH). Reports of cases of disease 

received by DPH are shared with AIP; these reports are used to identify potential cases and request isolates if 

not received by AIP. If an isolate is not available but was laboratory-confirmed and meets the case definition, 

the report is included as a case. 

AIP defines a case of invasive S. pneumoniae, H. influenzae, N. meningitidis, GAS or GBS as an isolate of the 

bacteria from a normally sterile site, including blood, cerebrospinal fluid, pleural fluid, peritoneal fluid or joint 

fluid that has been taken from a resident of Alaska. In addition, for GAS, laboratories are asked to submit 

isolates obtained from deep tissue infections (e.g., collected from surgical debridement of patients with 

necrotizing fasciitis).
Surveillance of Invasive Bacterial Disease in Alaska, 2016 6

Invasive Pneumococcal Disease (IPD) 

Overall Incidence

A total of 116 pneumococcal isolates were received at AIP in 2016. An additional 13 cases were detected 

through shared surveillance with the State DPH and 2 cases were reported by laboratories during the annual 

audit for a total of 131 cases of invasive pneumococcal disease. The overall rate for invasive pneumococcal 

disease in 2016 was 17.7 cases per 100,000 persons per year. Alaska rates for 2016 were higher than the 2016 

national projected rate of 9.4/100,000 [2] for Active Bacterial Core Surveillance (ABCs), a surveillance system 

that operates in 10 states and covers a population of up to 42 million persons. 

Month of Culture

Invasive Streptococcus pneumoniae cases were identified in each month of 2016. The largest number of cases 

(n=14) were reported in March and September. 

Race 

In 2016, the state population was comprised of 20% Alaska Native (AN) people (Alaska Native persons alone 

or in combination 147,699 non-Native persons 592,129) [1]. Of all reported S. pneumoniae cases in 2016, 56 

(43%) occurred in Alaska Native people; the age-adjusted rate was 41.3/100,000 persons per year. Seventy-five 

cases occurred in non-Native (NN) people, for an age-adjusted rate of 11/100,000 persons per year. The rate 

ratio of age-adjusted rates of S. pneumoniae disease for the Alaska Native population compared with the nonNative population in 2016 was 3.8. 

Table 2: IPD Cases by Race – Alaska, 2016 

Race 

Cases 

n (%) 

Age Adjusted 

Rate* % Male 

Deaths 

n (%) 

Alaska Native Persons 56 (43) 41.3 59% 2 (4)‡ 

Non-Native Persons† 75 (57)† 11.0 53% 11 (15)‡ 

Total 131 56% 13 (10) 

*Cases per 100,000 per percent distribution of Alaska 2010 population 

†Includes 10 cases for which race was unknown 

‡Outcome unknown in 1 AK Native case, 1 non-Native case 

0

5

10

15

Number of Cases

Figure 2: Invasive Pneumococcal Disease, by 

Month of Culture - Alaska, 2016
Surveillance of Invasive Bacterial Disease in Alaska, 2016 7

Region 

The highest percentage (66%) of IPD cases occurred in the Anchorage area in 2016. Rates of disease, however, 

were highest in the YK Delta (45.3/100,000 persons per year) and the Kotzebue region (23.2/100,000 persons 

per year). 

Age

Cases occurred in all age groups in 2016, with age ranging from 9 months to 89 years and a median age of 56 

years. Overall, the highest rates of disease occurred in adults aged 55-64 years and 65 years and older. 

 

When stratified by age and race, the highest rates of disease in 2016 occurred in Alaska Native adults 65 years 

and older (100.7/100,000 persons per year). 

Since the initiation of a pneumococcal 7-valent conjugate vaccine (PCV7) program in 2001, overall rates of 

invasive disease declined dramatically in children less than 2 years of age [3]. In 2008, the rate of IPD in 

children less than 2 years declined to 65.6/100,000 which was the lowest rate observed in this age group since 

introduction of the 7-valent vaccine. Following introduction of a 13-valent conjugate vaccine (PCV13) in 2010, 

rates of disease observed in children less than 2 years old declined to 18/100,000 in 2011. In 2012, however, 

0

20

40

60

0

20

40

60

80

100

Cases per 100,000

Number of Cases

Figure 3: Invasive Pneumococcal Disease, Cases 

& Rates by Region - Alaska, 2016

Cases

Rate

0

20

40

60

80

100

120

0

5

10

15

20

25

30

35

<2 2-4 5-18 19-54 55-64 65+

Cases per 100,000

Number of Cases

Age (yrs)

Figure 4: Invasive Pneumococcal Disease, Cases 

& Rates by Age Group & Race - Alaska, 2016

AN

Persons (#

cases)

NN

Persons (#

cases)

AN

Persons

(Rate)

NN

Persons

(Rate)
Surveillance of Invasive Bacterial Disease in Alaska, 2016 8

disease rates in this age group increased to 60.3/100,000 due to disease caused by serotypes not included in the 

current vaccine. In 2016, rates declined to 18.8/100,000. 

Although pneumococcal disease rates dropped initially in AK Native and non-Native children less than 2 years 

of age after introduction of PCV7, the rates of disease in AK Native children less than 2 years trended upward 

from a low of 93.6/100,000 in 2001 to 335.9/100,000 in 2006 (data not shown, historical trend). This increase 

in rates was due primarily to disease caused by serotypes not contained in PCV7 [4,5]. In 2009, rates of disease 

in AK Native children less than 2 years declined to 87.1/100,000 which was the lowest rate since the 

introduction of PCV7. After introduction of PCV13 in 2010, rates declined to 30.7/100,000 in 2011, however, 

increased to 177.5/100,000 in 2012. Rates have since declined to 35.1/100,000 in 2016. Rates of invasive 

disease in non-Native children less than 2 years declined during the same time period reaching 26.8/100,000 in 

2005, and following an increase to 64.4/100,000 in 2007, declined in 2008 to 6.2/100,000. In 2009, the rate of 

disease in non-Native children less than 2 years increased to 60.3/100,000, but declined to 13/100,000 in 2012 

with use of PCV13. Following an increase in 2013 (26.3/100,000), rates in non-Native children less than 2 

years were similar in 2014 (25.9/100,000), but declined in 2015 to 12.8/100,000 and remained the same in 2016 

(12.8/100,000). 

0

20

40

60

80

100

120

<2 2-4 5-18 19-54 55-64 65+

Cases per 100,000

Age (yrs)

Figure 5: Invasive Pneumococcal Disease by Age 

Group - Alaska, 2007-2016

2007

2008

2009

2010

2011

2012

2013

2014

2015

2016

0

50

100

150

200

250

<2 2-4 5-18 19-54 55-64 65+

Cases per 100,000

Age (yrs)

Figure 6: Invasive Pneumococcal Disease in 

Alaska Native Persons, by Age Group - Alaska, 

2007-2016

2007

2008

2009

2010

2011

2012

2013

2014

2015

2016
Surveillance of Invasive Bacterial Disease in Alaska, 2016 9

Clinical Presentation

The primary clinical presentation was determined by a review of the discharge diagnoses associated with the 

invasive bacterial illness in each patient’s individual medical record. In patients with multiple discharge 

diagnoses, the most serious diagnosis related to the pneumococcal infection was recorded as the primary clinical 

presentation. Pneumonia with bacteremia was the most common primary clinical presentation in 2016 (69%) 

followed by bacteremia (12%). Thirteen patients had a secondary pneumococcal-related diagnosis in 2016, 

including pneumonia with bacteremia (7), cellulitis (3), streptococcal toxic shock syndrome (1), cellulitis and 

necrotizing fasciitis (1), and cellulitis and osteomyelitis (1). 

In 2016, blood, which was used to identify 127 (97%) of 131 cases, was the most common source of a positive 

culture. Two cases each were identified from cerebrospinal fluid and joint fluid. 

Mortality 

In 2016, the overall case fatality ratio for S. pneumoniae in Alaska was 10% (13 deaths out of 129 cases for 

which outcome was known). The case fatality ratio for non-Natives was higher (15%, 11 deaths) than for AK 

0

50

100

150

200

250

<2 2-4 5-18 19-54 55-64 65+

Cases per 100,000

Age (yrs)

Figure 7: Invasive Pneumococcal Disease in NonNative Persons, by Age Group - Alaska, 2007-2016

2007

2008

2009

2010

2011

2012

2013

2014

2015

2016

90

16

7 4 4 4 2 2 1 1

0

20

40

60

80

100

Number of Cases

Figure 8: Primary Clinical Presentations of 

Invasive Pneumococcal Disease - Alaska, 2016

*with bacteremia
Surveillance of Invasive Bacterial Disease in Alaska, 2016 10

Natives (4%, 2 deaths). The highest case fatality ratio occurred in the 65 and older age category: 6 deaths, CFR 

19.4%. 

Serotype

Serotyping of IPD isolates is performed at AIP using internationally standardized methods. Serotype 

identification is based on the organism’s polysaccharide capsule, which is a principal virulence factor for 

pneumococci. This information provides a way to categorize organisms and to determine if the infection was 

due to a type that could be prevented by use of one of the available pneumococcal vaccines. Serotyping was 

performed on all of the S. pneumoniae cases for which an isolate was available. AIP received 116 isolates in 

2016 and 3 of those isolates were non-viable; 113 isolates were serotyped. 

Table 3: IPD Serotype Distribution by Race and Age Group – Alaska, 2016 

 Alaska Native Non-Native 

Serotype Total n (%) <2 2-4 5-18 19-64 65+ <2 2-4 5-18 19-64 65+ 

03 9 (8) - - - 1 - - - - 7 1 

04 1 (1) - - - - - - - - - 1 

06C 4 (4) - - - 1 - - - - 1 2 

07C 1 (1) - - - - - - - - - 1 

07F 2 (2) - - - 1 - - - - 1 - 

08 10 (9) - - 1 - 1 - - - 8 - 

09N 10 (9) - - - 3 1 - - - 6 - 

10A 9 (8) 1 - - 5 3 - - - - - 

11A 3 (3) - - - 1 - - - - - 2 

12F 6 (5) - - - 5 - - - - 1 - 

15A 3 (3) 1 - - - - - - - 2 - 

15C 3 (3) - - - 1 - - - - - 2 

16F 5 (4) - 1 - 2 - - - - 1 1 

17F 3 (3) - 1 - 1 - - - - 1 - 

19A 4 (4) - - - - 2 - - - 2 - 

19F 3 (3) - - - - - - - - 3 - 

20 11 (10) - - - 7 1 - - - 3 - 

21 1 (1) - - - - - - - - - 1 

22F 10 (9) - - 1 2 1 - - - 4 2 

23A 3 (3) - - - 2 - - - - 1 - 

23B 3 (3) - - - - - - - - 2 1 

31 2 (2) - - - 2 - - - - - - 

33F 3 (3) - - 1 - - 2 - - - - 

35B 2 (2) - - - - - - 1 - - 1 

38 2 (2) - - - - - - - - - 2 

Total 113 2 2 3 34 9 2 1 0 43 17 

0

5

10

15

20

25

0

1

2

3

4

5

6

7

<2 2-4 5-18 19-54 55-64 65+

Case Fatality Ratio (%)

Number of Deaths

Age (yrs)

Figure 9: Invasive Pneumococcal Deaths & Case 

Fatality Ratios by Age Group - Alaska, 2016

Deaths

CFR
Surveillance of Invasive Bacterial Disease in Alaska, 2016 11

In 2016, the most common pneumococcal serotypes were 20, (11 isolates, 10%), 8 (10 isolates, 9%), 9N (10 

isolates, 9%) and 22F (10 isolates, 9%). From 1986 through 2001, serotype 14 was the most common invasive 

pneumococcal serotype ranging from 7.4% to 23.5% of isolates. Following introduction in 2001 of PCV7 

which includes serotype 14, the proportion of serotype 14 isolates dropped to 1.5% of serotyped isolates in 2006 

and there were no serotype 14 cases in 2016. Disease caused by serotypes 7F and 19A, which are not included 

in the 7-valent conjugate vaccine, continually increased until the introduction of PCV13 in 2010 which does 

include these two serotypes. Although cases caused by 7F and 19A continue to occur, they are no longer the 

most common serotypes. The majority (73%) of serotype 20 cases, serotype 8 cases (80%), serotype 9N (80%) 

and serotype 22F cases (50%) occurred in the Anchorage area in 2016. 

 

Table 4: IPD Serotype Distribution by Region – Alaska, 2016 

Serotype 

Anchorage Arctic Slope Bristol Bay Interior Kotzebue Norton Sound Southeast YK Delta 

03 6 - - 2 - - - 1 

04 1 - - - - - - - 

06C 2 - - 2 - - - - 

07C 1 - - - - - - - 

07F 2 - - - - - - - 

08 8 - - 1 - - - 1 

09N 8 - - 1 - - 1 - 

10A 1 - - 1 2 - - 5 

11A 2 - - 1 - - - - 

12F 2 - - - - - 4 - 

15A 3 - - - - - - - 

15C 2 - - 1 - - - - 

16F 2 - - 2 - 1 - - 

17F 2 - - 1 - - - - 

19A 3 - - - - - 1 - 

19F 2 - - - - - 1 - 

20 8 - - - - - - 3 

21 1 - - - - - - - 

22F 5 - - 2 - - 2 1 

23A 2 - - 1 - - - - 

23B 2 - - 1 - - - - 

31 1 - - 1 - - - - 

33F 3 - - - - - - - 

35B 2 - - - - - - - 

38 2 - - - - - - - 

Unknown 13 - - 3 - 1 - 1 

Total 86 0 0 20 2 2 9 12 

Vaccine Serotypes

In 2001, PCV7 was included in the Alaska childhood vaccination schedule. This vaccine provided protection 

against the 7 most common pneumococcal serotypes causing invasive disease among children (types 4, 6B, 9V, 

14, 18C, 19F, 23F). In early 2010, PCV13 was introduced into the Alaska childhood vaccination schedule. 

This vaccine provided protection against the 7 pneumococcal serotypes contained in PCV7 plus six additional 
Surveillance of Invasive Bacterial Disease in Alaska, 2016 12

serotypes (1, 3, 5, 6A, 7F, 19A) that have caused invasive disease since the introduction of PCV7. The table 

below shows the proportion of invasive infections from 2016 that were due to serotypes found in PCV13. 

There were no cases of pneumococcal disease caused by serotypes contained in PCV13 in children less than 5 

years of age, the age group for which the vaccine is recommended. 

Table 5: Proportion of Invasive Isolates Contained in the PCV13 Vaccine by Age Group and Race – 

Alaska, 2016 

Age (yrs) Alaska Native (%) Non-Native (%) Total (%) 

<2 0 (0%) of 2 0 (0%) of 2 0 (0%) of 4 

2-4 0 (0%) of 2 0 (0%) of 1 0 (0%) of 3 

5+ 4 (9%) of 46 15 (25%) of 60 19 (18%) of 106 

Total 4 (8%) of 50 15 (24%) of 63 19 (17%) of 113 

For the year covered by this report, the 23-valent polysaccharide vaccine (Ps23V) was recommended in Alaska 

for all persons 65 years and older, and for persons over age 2 who are at higher risk for pneumococcal disease 

[5]. In addition, one dose of PCV13 was also recommended for persons 65 years and older. In 2016, for 

persons 65 years and older, 9 (35%) of 26 cases serotyped were potentially vaccine preventable invasive 

pneumococcal illnesses. 

Vaccine Failures 

In 2016, pneumococcal vaccine status was known for 125 (95%) of the 131 cases; 45% (n=56) of patients with 

known vaccine status did receive a pneumococcal vaccine prior to illness and 69 patients (55%) had no record 

of a pneumococcal vaccine. 

A PCV13 vaccine failure is defined as invasive pneumococcal disease caused by a serotype contained in PCV13 

in a child less than five years old who has had at least two doses of vaccine. There were no vaccine failures in 

2016. 

Potentially Preventable Deaths

Overall, 46% of all pneumococcal-related mortality in 2016 was potentially preventable with the use of the 23-

valent polysaccharide vaccine in persons over 5 years old; 46% of deaths were due to disease caused by

serotypes not contained in pneumococcal vaccines. 

Table 6: Potentially Vaccine Preventable IPD Deaths – Alaska, 2016 

Serotypes < 2 years 2-4 5-18 19-54 55-64 65+ Total 

PCV13 0 0 0 0 0 0 0 

Ps23V 0 0 0 0 4* (67%) 2* (33%) 6 (46%) 

Non-Vaccine 0 0 0 1 (100%) 1 (17%) 4 (67%) 6 (46%)

Unknown 0 0 0 0 1 (17%) 0 1 (8%) 

Total 0 0 0 1 6 6 13 

*One case was serotype 3 which is also contained in PCV13 

Six of the 13 deaths in 2016 from invasive S. pneumoniae were caused by serotypes contained in the Ps23V 

vaccine; two of the deaths were in individuals eligible for the vaccine. Both deaths occurred in a vaccinated 

individual; time since vaccination was 13 years for one case and 5 years for the second. 
Surveillance of Invasive Bacterial Disease in Alaska, 2016 13

Table 7: IPD, Serotypes of Fatal Cases – Alaska, 2016 

Serotype

Deaths 

n (%) 

Serotype 

Frequency (n) 

03†* 2 (22) 9 

07C 1 (100) 1 

08* 1 (10) 10 

10A* 1 (11) 9 

12F* 1 (17) 6 

16F 1 (20) 5 

17F* 1 (33) 3 

21 1 (100) 1 

23B 2 (67) 3 

35B 1 (50) 2 

†Serotypes contained in the 13-valent conjugate vaccine 

*Serotypes contained in the 23-valent polysaccharide vaccine 

Reported Risk Factors

The presence of one or more associated risk factors was reported in 82% of IPD cases in 2016. Cigarette 

smoking was the most prevalent risk factor observed in adults, followed by alcohol abuse and diabetes.

Table 8: Reported Risk Factors* Identified in IPD Cases – Alaska, 2016 

Risk Factor 

Adult Cases (≥ 18 years) 

n=121, Cases (%) 

Cigarette smoking 46 (38) 

Alcohol abuse 40 (33) 

Diabetes 20 (17) 

Chronic lung disease 16 (13) 

Injection drug use 6 (5) 

Immunosuppressive treatment 5 (4) 

Asplenia 0 (0) 

*More than one risk factor was identified in several cases 

Antibiotic Resistance

Susceptibility testing was performed on 113 isolates received in 2016. Cut points from the Minimum Inhibitory 

Concentration (MIC) Interpretive Standards were used to determine if an isolate was ‘susceptible’, 

‘intermediate’, or ‘resistant’ to the antibiotic being tested [7]. The MIC Interpretive Standards definitions of 

‘susceptible’, ‘intermediate’, and ‘resistant’ can be found in the Appendix. Results of the testing are presented 

in the following table. 

Table 9: Antibiotic Resistance in Invasive Streptococcus pneumoniae Isolates – Alaska, 2016 

Antibiotic Susceptible Intermediate Resistant I + R Total Tested 

Penicillin 96 (85%) 13 (11.5%) 4 (3.5%) 17 (15%) 113 

TMP-sulfa 99 (88%) 13 (11%) 1 (1%) 14 (12%) 113 

Erythromycin 94 (83%) 0 (0%) 19 (17%) 19 (17%) 113 

Ceftriaxone 109 (96%) 2 (2%) 2 (2%) 4 (4%) 113 

Tetracycline 107 (95%) 1 (1%) 5 (4%) 6 (5%) 113 

Chloramphenicol 112 (99%) 0 (0%) 1 (1%) 1 (1%) 113 

Vancomycin 113 (100%) 0 (0%) 0 (0%) 0 (0%) 113 

Levofloxacin 113 (100%) 0 (0%) 0 (0%) 0 (0%) 113 

Clindamycin 108 (96%) 0 (0%) 5 (4%) 5 (4%) 113 
Surveillance of Invasive Bacterial Disease in Alaska, 2016 14

Serotypes found in PCV7 and PCV13 are more likely to be non-susceptible to penicillin and erythromycin than 

non-vaccine serotypes. One potential benefit of the use of these vaccines was an anticipated decline in 

antibiotic resistance among circulating pneumococci. Following the initiation of the PCV7 vaccine in 2001, 

antibiotic resistance among invasive pneumococci dropped. During 2003, TMP-sulfa and penicillin resistance 

increased, however, following an increase in disease caused by serotype 19A. This serotype is included in the 

PCV13 vaccine; decreasing proportions of isolates resistant to most antibiotics tested may be due to the 

introduction of the vaccine. However, the proportion of isolates resistant to erythromycin has increased which 

is a trend that was also seen after the introduction of PCV7 [8]. 

0

5

10

15

20

25

30

35

Percent Non-Susceptible

Year

Figure 10: Trends in Antibiotic Non-Susceptibility Among 

Invasive Pneumococcal Isolates - Alaska, All Ages, 1996 -

2016

Penicillin

Erythro

TMP-Sulfa

Tet
Surveillance of Invasive Bacterial Disease in Alaska, 2016 15 

Invasive Haemophilus influenzae

Overall Incidence 

In 2016, there were 19 cases of invasive Haemophilus influenzae in Alaska, for a statewide rate of 2.6/100,000 

persons per year. This rate is higher than the ABCs 2016 national projected rate of 1.99/100,000 persons per 

year [9]. There were 5 deaths associated with H. influenzae in 2016, for a case fatality ratio of 26%. 

Month of Culture 

Cases of invasive H. influenzae occurred throughout 2016; the largest number of cases (n=4) occurred in 

January. 

Region 

The highest rates of disease caused by invasive H. influenzae in 2016 were in the YK Delta region, 

18.9/100,000 (5 cases), and the Bristol Bay region, 14.1/100,000 (1 case). Although a large number of cases 

occurred in the Anchorage area (10 cases), the rate was much lower (2/100,000). 

0

1

2

3

4

5

Number of Cases

Month of Culture

Figure 11: Haemophilus influenzae Disease by 

Month of Culture - Alaska, 2016

0

10

20

0

2

4

6

8

10

12

Cases per 100,000

Number of Cases

Figure 12: Invasive Haemophilus influenzae, 

Cases & Rates by Region - Alaska, 2016

Cases

Rate
Surveillance of Invasive Bacterial Disease in Alaska, 2016 16 

Race 

Table 10: Invasive Haemophilus influenzae Cases by Race – Alaska, 2016 

Race Cases n (%) 

Age Adjusted 

Rate* % Male 

Deaths 

n (%) 

Alaska Native Persons 10 (53%) 6.0 70% 3 (30%) 

Non-Native Persons 9 (47%) 1.4 44% 2 (22%) 

Total 19 58% 5 (26%) 

*Cases per 100,000 per percent distribution of Alaska 2010 population 

In 2016, 53% of the cases occurred in Alaska Native persons. Age-adjusted rates were calculated for Alaska 

Native and non-Native persons. The age-adjusted rate ratio of H. influenzae disease for the Alaska Native 

population compared with the non-Native population in 2016 was 4.3. 

Age 

H. influenzae patients ranged in age from 1 month to 87 years in 2016 (median 28.6 years). Overall, the highest 

rates of disease occurred in children less than 2 years old (32.8/100,000). 

Rates of disease in Alaska Native versus non-Native populations by age group were variable; overall numbers 

of cases and rates by race and age group are presented in Figure 14. The highest rates of disease occurred in 

Alaska Native children less than two years of age and Alaska Native adults 65+ years of age, 105.4/100,000 

persons per year and 18.3/100,000 persons per year, respectively. 

0

10

20

30

40

<2 2-4 5-18 19-54 55-64 65+

Cases per 100,000

Age (yrs)

Figure 13: Invasive Haemophilus influenzae by 

Age Group - Alaska, 2016
Surveillance of Invasive Bacterial Disease in Alaska, 2016 17 

Clinical Presentation 

The primary clinical presentation was determined by a review of the discharge diagnoses in each patient’s 

individual medical record associated with the invasive bacterial illness. For cases with more than one diagnosis, 

the most serious H. influenzae-related diagnosis was recorded as the primary clinical presentation. In 2015, 

pneumonia with bacteremia was the most common presentation (47% of cases). 

Sixteen (84%) H. influenzae isolates were from blood samples in 2016, two were from cerebrospinal fluid and 

one was from peritoneal fluid. 

Table 11: Primary Clinical Presentation of Invasive Haemophilus influenzae - Alaska, 2016 

Primary Presentation n (%) 

Pneumonia* 9 (47%) 

Bacteremia 4 21%) 

Meningitis 3 (16%) 

Peritonitis 2 (11%) 

Cellulitis* 1 (5%) 

Total 19 

*with bacteremia 

Serotypes 

All isolates received at AIP are serotyped; 18 (95%) cases in 2016 had isolates and were serotyped. The 

bacterial capsule is the basis for serotyping and is the primary virulence factor. Serotype b was the most 

common serotype in the past, but its prevalence has decreased with use of the childhood Hib vaccine. 

Surveillance of serotypes is important for monitoring vaccine effectiveness and emergence of non-vaccine 

serotypes. 

0

20

40

60

80

100

120

0

1

2

3

4

5

6

7

<2 2-4 5-18 19-54 55-64 65+

Cases per 100,000

Number of Cases

Age (yrs)

Figure 14: Invasive Haemophilus influenzae, Cases & 

Rates by Age Group & Race - Alaska, 2016

AN Persons

# Cases

NN Persons

# Cases

AN Persons

Rate

NN Persons

Rate
Surveillance of Invasive Bacterial Disease in Alaska, 2016 18 

Table 12: Serotypes of Invasive Haemophilus influenzae Cases by Race – Alaska, 2016 

 Alaska Native Persons Non-Native Persons 

Serotype Total n (%) <2 2-18 19-64 65+ <2 2-18 19-64 65+ 

a 6 (32) 4 - - 1 - 1 - - 

b 1 (5) 1 - - - - - - - 

f 3 (16) 1 - - - 1 - 1 - 

NT* 8 (42) - 1 - 1 - - 2 4 

Unknown 1 (5) - - 1 - - - - - 

Total 19 6 1 1 2 1 1 3 4 

*Non-typeable 

Hib

In recent years, the prevalence of H. influenzae type b has declined due to increased use of a childhood vaccine 

against this serotype. There was one case of Hib in a child less than 5 years old in 2016; the child was 2 months 

old and had not yet received any vaccine. 

Hia 

Prior to 2002, H. influenzae type a (Hia) had not been detected in Alaska. Following an outbreak in 2003 [10], 

cases have occurred sporadically until 2010 when an outbreak began in the YK Delta and continued through 

2011 [11]. Six cases of Hia were detected in 2016; 83% occurred in AK Native people. The rate of invasive 

disease caused by Hia in AK Native children less than 2 years old for 2016 was 70.2/100,000. 

Antibiotic Resistance 

Eighteen H. influenzae isolates received at AIP were tested for susceptibility to ampicillin, chloramphenicol, 

ceftriaxone and TMP/sulfa. All isolates tested were susceptible to ceftriaxone and chloramphenicol, 6 isolates 

were resistant to ampicillin (1 intermediate, 5 fully resistant), and 9 isolates were resistant to TMP/sulfa (4 

intermediate and 5 fully resistant). 
Surveillance of Invasive Bacterial Disease in Alaska, 2016 19 

Invasive Neisseria meningitidis

Overall Incidence

Seven cases of invasive Neisseria meningitidis were reported to AIP in 2016, for an overall rate of 1/100,000. 

The Alaska rate is higher than the ABCs 2016 national projected rate of 0.12/100,000 [12]. There were 3 

invasive N. meningitidis-related deaths in Alaska in 2016, for a case fatality ratio of 43%. 

Race 

Table 13: Invasive Neisseria meningitidis Cases by Race – Alaska, 2016 

Race 

Cases 

 n (%) 

Age 

Adjusted 

Rate* 

% 

Male 

Deaths 

n (%) 

Alaska Native Persons 5 (71) 2.8 60 3 (60) 

Non-Native Persons 2 (29) 0.3 100 0 (0) 

Total 7 71 3 (43) 

*Cases per 100,000 per percent distribution of Alaska 2010 population 

In 2016, 71% of the cases occurred in Alaska Native persons. Age-adjusted rates were calculated for Alaska 

Native and non-Native persons. The age-adjusted rate ratio of N. meningitidis disease for the Alaska Native 

population compared with the non-Native population in 2016 was 9.3. 

 
Surveillance of Invasive Bacterial Disease in Alaska, 2016 20 

Invasive group A Streptococcus

Overall Incidence

A total of 146 cases of invasive group A Streptococcus (GAS) were reported to AIP in 2016. The overall rate 

of invasive GAS disease in the state of Alaska was 19.7/100,000 persons per year. The Alaska rate is higher 

than the ABCs 2016 national projected rate of 5.8/100,000 [13]. In 2016, there were 16 GAS-related deaths for 

a case fatality ratio of 11%. 

Month of Culture 

Cases of group A Streptococcus occurred throughout the year in 2016; the largest number of cases (n=22) 

occurred in December. 

Race

In 2016, 64% of invasive GAS cases in Alaska occurred in the Alaska Native population. The age-adjusted rate 

ratio of invasive GAS disease for the Alaska Native population compared with the non-Native population in 

2016 was 8.2. 

Table 14: Invasive group A Streptococcus Cases by Race – Alaska, 2016 

Race 

Cases 

n (%) 

Age Adjusted 

Rate* % Male 

Deaths 

n (%) 

Alaska Native 

Persons 

93 (64%) 68.2 62% 10 (11%) 

Non-Native 

Persons 

53† (36%) 8.3 63% 6 (11%) 

Total 146 64% 16 (11%) 

*Cases per 100,000 per percent distribution of Alaska 2010 population 

†Includes 5 cases for which race is unknown 

Region 

One hundred one (69%) of the 146 invasive group A Streptococcus cases in 2016 were reported in the 

Anchorage area, 19 cases in the YK Delta, 15 cases in the Interior, Southeast, 4 cases in the Kotzebue region, 3 

0

5

10

15

20

25

Number of Cases

Month of Culture

Figure 15: Invasive group A Streptococcus, by 

Month of Culture - Alaska, 2016
Surveillance of Invasive Bacterial Disease in Alaska, 2016 21 

cases in the Southeast, 2 cases in the Arctic Slope and one case each in Bristol Bay and Norton Sound. The 

highest rates of disease occurred in the YK Delta (71.6/100,000) and the Kotzebue region (46.4/100,000). 

Age

Patients with invasive group A Streptococcus reported in 2016 ranged in age from 3 months to 92 years old; the 

median age was 50.9 years. Highest rates of disease occurred in children less than 2 years old (42.2/100,000). 

When stratified by race, the highest rates of invasive group A streptococcal disease occurred in Alaska Native 

adults 55-64 years old (147.5/100,000 persons per year). The highest GAS disease rate in the non-Native 

population occurred in adults 65 years and older (17.6/100,000 persons per year). 

0

10

20

30

40

50

60

70

80

0

20

40

60

80

100

120

Number of Cases

Cases per 100,00

Figure 16: Invasive GAS Disease, Cases & Rates 

by Region - Alaska, 2016

Cases

Rate

0

5

10

15

20

25

30

35

40

45

<2 2-4 5-18 19-54 55-64 65+

Cases per 100,000

Age (yrs)

Figure 17: Invasive group A Streptococcus by Age 

Group - Alaska, 2016
Surveillance of Invasive Bacterial Disease in Alaska, 2016 22 

Clinical Presentation

The primary clinical presentation was determined by a review of the discharge diagnoses in each patient’s 

individual medical record associated with the invasive bacterial illness. In cases with multiple discharge 

diagnoses, the most serious diagnosis related to the GAS infection was recorded as the primary clinical 

presentation. Table 18 shows the primary clinical presentations of invasive group A Streptococcus in Alaska 

for 2016. 

Group A Streptococcus was isolated from blood samples in 78 (53%) of 146 cases, 43 (29%) from surgical 

specimens, 10 from joint fluid, 4 each from bone, pleural fluid and abscesses, 2 from wounds, and one from 

CSF. 

 

Table 15: Primary Clinical Presentations of Invasive group A Streptococcus – Alaska, 2016 

Primary Presentation n (%) 

Cellulitis* 45 (31%) 

Pneumonia* 22 (15%) 

Necrotizing fasciitis 19 (13%) 

Bacteremia 19 13%) 

Septic arthritis 11 (8%) 

Osteomyelitis 8 (5%) 

Strep toxic shock 7 (5%) 

Meningitis 2 (1%) 

Peritonitis 1 (<1%) 

Empyema 1 (<1%) 

Endocarditis 1 (<1%) 

Bursitis 1 (<1%) 

Other 9 (6%) 

Total 146 

*with bacteremia

Reported Risk Factors

The presence of one or more associated risk factors was reported in 86% of invasive GAS cases in 2016. 

Alcohol abuse was the most prevalent risk factor observed in adults, followed by cigarette smoking and

diabetes. 

0

20

40

60

80

100

120

140

160

0

10

20

30

40

50

60

<2 2-4 5-18 19-54 55-64 65+

Cases per 100,000

Number of Cases

Age (yrs)

Figure 18: Invasive group A Streptococcus, Cases 

& Rates by Age Group & Race - Alaska, 2016

AN Persons

# Cases

NN Persons

# Cases

AN Persons

Rate

NN Persons

Rate
Surveillance of Invasive Bacterial Disease in Alaska, 2016 23 

Table 16: Reported Risk Factors Identified in Invasive GAS Cases – Alaska, 2016* 

Medical Condition/Risk 

Factor 

Adult Cases (≥ 18 years) 

n=128, Cases (%) 

Alcohol abuse 65 (51%) 

Cigarette smoking 53 (42%) 

Diabetes 18 (14%) 

Chronic lung disease 17 (13%) 

Injection drug use 15 (12%) 

Immunosuppressive treatment 6 (5%) 

Asplenia 0 (0%) 

*More than one risk factor was identified in several cases 

Molecular Typing 

Strain characterization of GAS has traditionally been based on serological identification of the M protein which 

is a major surface protein and an important GAS virulence factor. In the mid-1990s, many reference labs 

started using a molecular approach based on sequencing of the N-terminal region of the M protein gene (emm

gene). To date, more than 200 different emm types have been reported. While there are currently no vaccines 

available to protect against invasive GAS disease, baseline data on the burden of GAS disease to include emm

typing are critical to evaluate the potential utility of any candidate vaccines.

In 2016, 137 invasive GAS isolates were emm typed at AIP. The most common emm types were emm 26 (28%) 

and emm 11 (25%). The isolates identified as emm 26 were part of an outbreak that occurred in Alaska 

beginning in 2016 [14]. The following graph shows emm typing trends over time. Strains that totaled ≤ 10 

isolates over the time period were not included. 

Antibiotic Resistance 

One hundred thirty-seven GAS isolates received at AIP were tested for susceptibility to penicillin, ceftriaxone, 

erythromycin, vancomycin, levofloxacin and clindamycin. All isolates tested were susceptible to penicillin, 

ceftriaxone, and vancomycin and levofloxacin. Thirty-six isolates were resistant to erythromycin; 33 of those 

0

20

40

60

80

100

120

140

160

2001200220032004200520062007200820092010201120122013201420152016

Number of Cases

Figure 19: Invasive group A Streptococcus emm 

Typing Trends - Alaska, 2001-2016 Unknown

108

101

92

91

89

87

82

73

49

41

28

26

12

11

5

4

3

1
Surveillance of Invasive Bacterial Disease in Alaska, 2016 24 

were emm type 11, two were emm type 91 and one was emm type 80. Three emm type 11 isolates and one emm

type 91 isolate were also resistant to clindamycin. 
Surveillance of Invasive Bacterial Disease in Alaska, 2016 25 

Invasive group B Streptococcus

Overall Incidence

A total of 68 cases of invasive group B Streptococcus (GBS) were reported to AIP in 2016. The overall rate of 

invasive GBS disease in the state of Alaska was 9.2/100,000 persons per year. The Alaska rate is similar to the 

ABCs 2016 national projected rate of 9.6/100,000 [15]. In 2016, there were four GBS-related deaths for a case 

fatality ratio of 6.1%. 

Month of Culture

Cases of group B Streptococcus occurred throughout the year; the largest number of cases (n=13) occurred in 

March. 

 

Race

In 2016, 28% of invasive group B Streptococcus cases in Alaska occurred in the Alaska Native population. The 

age-adjusted rate ratio of invasive GBS disease for the Alaska Native population compared with the non-Native 

population in 2016 was 1.9. 

Table 17: Invasive group B Streptococcus Cases by Race – Alaska, 2016 

Race 

Cases 

n (%) 

Age Adjusted 

Rate* % Male 

Deaths 

n (%) 

Alaska Native Persons 19 (28) 14.3 47 2 (11) 

Non-Native Persons 49 (72)‡ 7.5 61 2 (4)† 

Total 68 57 4 (6) 

*Cases per 100,000 per percent distribution of Alaska 2010 population 

†Outcome unknown in 2 cases 

‡Includes 5 cases for which race was unknown 

 

0

2

4

6

8

10

12

14

Number of Cases

Month of Culture

Figure 20: Invasive group B Streptococcus, by 

Month of Culture - Alaska, 2016
Surveillance of Invasive Bacterial Disease in Alaska, 2016 26 

Region 

In 2016, 50 (74%) of the 68 reported GBS cases occurred in Anchorage; 11 cases were reported in the Interior, 

five cases in Southeast and one case each in the Kotzebue and Norton Sound regions. The highest rates of 

disease occurred in the Kotzebue region (11.6/100,000) and Anchorage (10.2/100,000). 

Age

Patients with invasive group B Streptococcus reported in 2016 ranged in age from newborn to 88 years old; the 

median age was 55.2 years. Highest rates of disease overall occurred in persons 65 years and older 

(27.9/100,000 persons per year). 

 

When stratified by race, the highest rates of disease occurred in AK Native persons 55-64 years old and 65 

years and older, 35.1/100,000 persons per year and 64.1/100,000 persons per year, respectively. There was one 

case of early-onset disease (less than 7 days old) for a rate of 0.1 cases per 1,000 live births. 

Clinical Presentation

The primary clinical presentation was determined by a review of the discharge diagnoses in each patient’s 

individual medical record associated with the invasive bacterial illness. In cases with multiple discharge 

0

5

10

15

20

25

30

<2 2-4 5-18 19-54 55-64 65+

Cases per 100,000

Age (yrs)

Figure 21: Invasive group B Streptococcus by Age 

Group - Alaska, 2016

0

10

20

30

40

50

60

70

0

5

10

15

20

25

<2 2-4 5-18 19-54 55-64 65+

Cases per 100,000

Number of Cases

Age (yrs)

Figure 22: Invasive group B Streptococcus, Cases & 

Rates by Age Group & Race - Alaska, 2016

AN Persons

# Cases

NN Persons

# Cases

AN Persons

Rate

NN Persons

Rate
Surveillance of Invasive Bacterial Disease in Alaska, 2016 27 

diagnoses, the most serious diagnosis related to the GBS infection was recorded as the primary clinical 

presentation. In 2016, the most common clinical presentations were cellulitis and bacteremia which occurred in 

24 (35%) and 15 (22%) cases, respectively. 

Group B Streptococcus was isolated from blood in 49 (72%) of 68 cases in 2016; 8 cases were isolated from 

surgical specimens, 6 cases from joint fluid, and one each from peritoneal fluid, pericardial aspirate, placenta, 

abscess and bone. 

Table 18: Primary Clinical Presentations of Invasive group B Streptococcus – Alaska, 2016 

*with bacteremia

Associated Risk Factors

The presence of one or more associated risk factors was reported in 91% of invasive GBS cases in 2016. 

Diabetes was the most prevalent risk factor observed in adults followed by chronic lung disease and cigarette 

smoking. 

Table 19: Associated Risk Factors Identified in Adult Invasive GBS Cases – Alaska, 2016* 

Medical Condition/Risk 

Factor 

Adult Cases (≥ 18 years) 

n=64, Cases (%) 

Diabetes 38 (59%) 

Chronic lung disease 14 (22%) 

Cigarette smoking 10 (16%) 

Alcohol abuse 7 (11%) 

Immunosuppressive treatment 2 (3%) 

Asplenia 1 (2%) 

Injection drug use 0 (0%) 

*More than one risk factor was identified in several cases 

Antibiotic Resistance

Susceptibility testing was performed on 59 GBS isolates received in 2016. Results of the testing are presented 

in the following table. 

Primary Presentation n (%) 

Cellulitis* 24 (35) 

Bacteremia 15 (22) 

Pneumonia* 9 (13) 

Osteomyelitis 8 (12) 

Septic arthritis 5 (7) 

Meningitis 2 (3) 

Endocarditis 1 (1.5) 

Pericarditis 1 (1.5) 

Amnionitis 1 (1.5) 

Septic abortion 1 (1.5) 

Peritonitis 1 (1.5) 

Total 68 
Surveillance of Invasive Bacterial Disease in Alaska, 2016 28 

Table 20: Antibiotic Resistance in Invasive group B Streptococcus Isolates – Alaska, 2016 

Antibiotic Susceptible Intermediate Resistant I + R Total Tested 

Penicillin 59 (100%) 0 (0%) 0 (0%) 0 (0%) 59 

Ceftriaxone 59 (100%) 0 (0%) 0 (0%) 0 (0%) 59 

Erythromycin 30 (51%) 0 (0%) 29 (49%) 29 (49%) 59 

Vancomycin 59 (100%) 0 (0%) 0 (0%) 0 (0%) 59 

Levofloxacin 59 (100%) 0 (0%) 0 (0%) 0 (0%) 59 

Clindamycin 40 (68%) 1 (2%) 17 (29%) 18 (31%) 59 

All isolates tested were susceptible to penicillin, ceftriaxone, vancomycin and levofloxacin. Resistance to 

erythromycin and clindamycin was seen in 49% and 31%, respectively, of isolates tested. The one early onset 

cases did not have an isolate available for testing.
Surveillance of Invasive Bacterial Disease in Alaska, 2016 29 

References 

1. State of Alaska, Department of Labor & Workforce Development. From 

http://laborstats.alaska.gov/pop/popest.htm

2. Centers for Disease Control and Prevention. 2016. Active Bacterial Core Surveillance Report, Emerging 

Infections Program Network, Streptococcus pneumoniae, 2016.

3. Hennessy TW, Singleton RJ, Bulkow LR, Bruden DL, Hurlburt DA, Parks, D, Moore M, Parkinson AJ, 

Schuchat A, Butler JC. Impact of heptavalent pneumococcal conjugate vaccine on invasive disease; 

antimicrobial resistance and colonization in Alaska Natives: progress towards elimination of a health 

disparity. Vaccine 2005;23:5464-73. 

4. Singleton RJ, Hennessy TW, Bulkow LR, Hammitt LL, Zulz T, Hurlburt DA, Butler JC, Rudolph K, 

Parkinson A. Invasive pneumococcal disease caused by nonvaccine serotypes among Alaska Native 

children with high levels of 7-valent pneumococcal conjugate vaccine coverage. JAMA 

2007;297(16):1784-92. 

5. Wenger JD, Zulz T, Bruden D, Singleton R, Bruce MG, Bulkow L, Parks D, Rudolph K, Hurlburt D, Ritter 

T, Klejka J, Hennessy T. Invasive pneumococcal disease in Alaskan children: impact of the seven-valent 

pneumococcal conjugate vaccine and the role of water supply. Pediatr Infect Dis J 2010;29: 251-256. 

6. State of Alaska, Department of Health & Human Services. Retrieved 5/2/16 from 

http://www.epi.hss.state.ak.us/bulletins/docs/b2009_24.pdf

7. Clinical and Laboratory Standards Institute (CLSI). Performance Standards for Antimicrobial Susceptibility 

Testing; Nineteenth Informational Supplement. 2009; 29(3): M100-S19. p.21. 

8. Rudolph K, Bulkow L, Bruce M, Zulz T, Reasonover A, Harker-Jones M, Hurlburt D, Hennessy T. 

Molecular resistance mechanisms of macrolide-resistant invasive Streptococcus pneumoniae isolates from

Alaska, 1986 to 2010. Antimicrobial Agents and Chemotherapy 2013;57 (11): 5415-22. 

9. Centers for Disease Control and Prevention. 2016. Active Bacterial Core Surveillance Report, Emerging 

Infections Program Network, Haemophilus influenzae, 2016. 

10. Hammitt LL, Block S, Hennessy TW, DeByle C, Peters H, Parkinson A, Singleton R, Butler JC. Outbreak 

of invasive Haemophilus influenzae serotype a disease. Pediatr Infect Dis J 2005;24(5): 453-6. 

11. Bruce MG, Zulz T, DeByle C, Singleton R, Hurlburt D, Bruden D, Rudolph K, Hennessy T, Klejka J, 

Wenger JD. Haemophilus influenzae serotype a invasive disease, Alaska, USA, 1983-2011. Emerg Infect 

Dis 2013;19(6): 932-7. 

12. Centers for Disease Control and Prevention. 2016. Active Bacterial Core Surveillance Report, Emerging 

Infections Program Network, Neisseria meningitidis, 2016. 

13. Centers for Disease Control and Prevention. 2016. Active Bacterial Core Surveillance Report, Emerging 

Infections Program Network, Group A Streptococcus, 2016. 

14. Alaska Section of Epidemiology Bulletin. Outbreak of a Rare Subtype of Group A Streptococcus — Alaska, 

2016–2017. Available at: http://epibulletins.dhss.alaska.gov/Document/Display?DocumentId=1938 
Surveillance of Invasive Bacterial Disease in Alaska, 2016 30 

15. Centers for Disease Control and Prevention. 2016. Active Bacterial Core Surveillance Report, Emerging 

Infections Program Network, Group B Streptococcus, 2016. 
Surveillance of Invasive Bacterial Disease in Alaska, 2016 31 

Appendix 

MIC Interpretive Standards Definitions: 

CLSI [7] provides recommended interpretive categories for various Minimum Inhibitory Concentration values 

(cut points) for each organism/antibiotic combination which are defined as follows: 

1. Susceptible (S): 

The “susceptible” category implies that isolates are inhibited by the usually achievable concentrations of 

antimicrobial agent when the recommended dosage is used for the site of infection. 

2. Intermediate (I): 

The “intermediate” category includes isolates with antimicrobial agent MICs that approach usually attainable 

blood and tissue levels and for which response rates may be lower than for susceptible isolates. The 

“intermediate” category implies clinical efficacy applicability in body sites where the drugs are physiologically 

concentrated (e.g., quinolones and β-lactams in urine) or when a higher dosage of a drug can be used (e.g., βlactams). The “intermediate” category also includes a buffer zone which should prevent small, uncontrolled 

technical factors from causing major discrepancies in interpretations, especially for drugs with narrow 

pharmacotoxicity margins. 

3. Resistant (R): 

Resistant strains are not inhibited by the usually achievable concentrations of the agent with normal dosage 

schedules, and/or that demonstrate MICs or zone diameters that fall in the range where specific microbial 

resistance mechanisms are likely (e.g., β-lactamases) are likely, and clinical efficacy of the agent against the 

isolate has not been reliably shown in treatment studies.