Minnesota Department of Health (MDH) Bug Bytes

April 8, 2004
Vol. 5: No. 3


Topics in this Issue:
1. Measles Alert
2. GAS in Nursing Homes
3. Changing Epidemiology of Invasive Pneumococcal Disease Among Older Adults
4. Haemophilus influenzae Antibiotic Susceptibility
5. HUS Due to Non-O157 Shiga Toxin Producing E. coli

1. Measles Alert
Three cases of measles have been reported by the Iowa Department of Public Health (IDPH). The index case traveled to India with 30 other students and supervisors from an Iowa college. A high percentage of these students were unvaccinated due to non-medical exemptions and six students contracted measles in India. The IDPH recommended that the six infectious students stay in India for at least 4 days after rash onset and that the non-immunized, exposed students stay in India for at least 18 days after the last possible exposure. The index case was an unvaccinated contact who traveled from New Delhi through Amsterdam and the Detroit Metro Airport to Cedar Rapids, Iowa on March 12. During travel he had a cough and conjunctivitis.

The CDC notified us of several residents who had traveled on these flights. All known Minnesota contacts have been advised of the exposure and have reported measles immunity and no measles-like illness. The IDPH has reported two additional cases of measles and have identified specific guidelines surrounding potential exposures to those cases. This information is available at: http://www.idph.state.ia.us/eedo/measles.asp and http://www.cdc.gov/mmwr/PDF/wk/mm5311.pdf (PDF: 343KB/ 24 pages). Susceptible patients exposed to these cases would potentially develop symptoms on or before April 14, 2004.

Additionally an outbreak of measles has been reported in Mexico with 24 suspect and 15 confirmed cases. On April 7, the Seattle and King County Public Health Department reported a laboratory confirmed measles case in a recently adopted child from China and four suspect cases residing in King County, Washington. Providers are encouraged to consider measles in persons presenting with rash illness, especially those with a recent travel history to the aforementioned regions.

Measles is a highly infectious rash illness that can result in complications such as pneumonia, encephalitis, and death. Persons are considered susceptible if they were born in or after 1957 and have not had two doses of measles vaccine, or have not had physician diagnosed measles disease. An estimated 92% of Minnesotan children have received a measles containing vaccine by 24 months of age.

If measles is suspected in a patient, specimens should be submitted to us as soon as possible. The following specimens should be collected:

  • Blood collected on or after day four of rash for measles IgM antibody
  • Blood collected as soon as possible and 2-4 weeks after onset of rash for acute and convalescent measles IgG antibody (run as paired sera)
  • Urine, nasopharyngeal aspirates, blood, or throat swabs collected as soon as possible after rash onset for measles viral culture

Please contact the Minnesota Department of Health at 651-201-5414 with questions regarding specimen submission or disease reporting.

2. GAS in Nursing Homes
Invasive disease due to group A streptococcus (GAS) re-emerged in the 1980s. Advanced age and chronic conditions such as diabetes are risk factors for developing invasive disease. At least 15 outbreaks of invasive GAS disease in long-term care facilities (LTCF) have been described in the literature since 1983.

We have been conducting active statewide laboratory-based surveillance for invasive GAS disease since 1995 as part of our Emerging Infections Program (EIP). From April 1995 through 2003, 1,419 cases of invasive disease were reported in Minnesota residents; 136 (10%) of these cases were known to be LTCF residents. Eighty-five percent of the LTCF cases had positive blood cultures for GAS and 30% of them died. Thirty-six (26%) of the LTCF cases were identified as being part of a cluster (2 or more cases occurring in the same LTCF less than 18 months apart having pulsed-field gel electrophoresis [PFGE] patterns within a 2-band difference). Fourteen clusters were identified with 2-5 cases per cluster.

Twenty-three LTCFs had more than one case. The median interval between two cases in a facility having matching PFGE subtypes was 2 months while the median interval between cases with different subtypes was 3 years. Twenty-one of 24 (88%) of the cases occurring within 15 months of each other in a facility had matching PFGE subtypes.

We collected throat cultures from staff and residents on the involved units of two LTCFs experiencing outbreaks. Those with positive GAS cultures were treated with antibiotics and no further cases were seen in either facility. We used to contact a LTCF when a second case was observed in that facility. We've observed that these facilities were often unaware that any of their residents had GAS disease; we now contact a LTCF anytime a single case has been identified. Infection control staff are encouraged to conduct retrospective surveillance, looking for other possible cases of GAS disease (including noninvasive infections), and prospective surveillance, collecting cultures for suspicious infections whenever possible. Staff education about GAS disease, stressing the importance of hand hygiene, implementation of appropriate infection control precautions, and not working while ill with possible streptococcal infections, is also emphasized.

Thanks to our EIP partners (clinicians, laboratories, and infection control professionals) who helped gather these data and respond to disease clusters. This information was presented at the recent International Conference on Emerging Infectious Diseases. We hope the data will stimulate discussion of the formulation for national guidelines for the control of GAS disease in LTCFs.

3. Changing Epidemiology of Invasive Pneumococcal Disease among Older Adults
Our EIP site is just one of now 11 sites in the U.S. We recently examined EIP data on invasive pneumococcal disease (IPD), in adults >50 years, for the years 1998-2002 from Minnesota and also from 7 other EIP sites. The purpose was to look for changes in disease incidence in the older and elderly age groups that might be related to use of the new pediatric pneumococcal conjugate vaccine (Prevnar) which was licensed in 2000. This vaccine not only prevents disease in children, but it reduces their nasopharyngeal carriage of the vaccine-included pneumococcal strains (serotypes). Since pneumococci carried in the throats of young children are a major reservoir for this pathogen, it has been hypothesized that this vaccine might indirectly reduce disease in unvaccinated children and adults via herd immunity.

Rates of IPD are going down in this older age group; in 2002 rates were 28% lower in persons > 50 years than these rates in 1998-99, the years before vaccine licensure. Rates declined most for those aged 65-74 (-31%) and 75-84 (-34%). Rates declined to about the same extent in blacks and whites, though the rate for blacks (57/100,000) aged 65 and older in 2002 was still considerably higher than the rate for whites in this age group (42/100,000). Rates of death following an episode of IPD went down, but to a smaller degree than the overa0 as diabetes are risk factors for developing invll decrease in cases. Rates of pneumococcal bacteremic pneumonia went down significantly in those aged 65-84. Rates of bacteremia without a focus of infection, went down significantly in the same age group, and also among those aged 50-64, and > 85 years. Rates of meningitis did not appear to change. By 2002, rates of IPD in those > 50 declined significantly in 7 of the 8 surveillance sites.

As part of EIP surveillance, invasive pneumococcal isolates are submitted and serotyped at the MDH and CDC laboratories. Using these data, we found that while rates of IPD due to any of the 7 serotypes included in the new conjugate vaccine dropped, rates due to any of 16 serotypes included in the adult pneumococcal polysaccharide vaccine but not included in Prevnar, stayed about the same. Also, rates due to serotypes not included in either vaccine did not change appreciably. This, combined with the relatively consistent and progressive decreases in rates over the years 2000-2002 led us to conclude that the changes we are seeing in IPD incidence in older and elderly adults, are primarily due to use of Prevnar.

This analysis is a good example of the strength of population-based data collection that we do, with your help, as EIP partners. Here, we assessed the impact of a new vaccine on actual population-based rates in a way that couldn't be done in a single hospital, or even in a large vaccine trial.

4. Haemophilus influenzae Antibiotic Susceptibility
Haemophilus influenzae (Hi) is a common cause of invasive disease, particularly among the elderly. In the U.S., 20-40% of all Hi strains are resistant to ampicillin by virtue of their ability to produce ß-lactamase (ßL). Occasionally, ampicillin resistance arises through a different mechanism resulting in ßL-negative, ampicillin-resistant isolates. As part of our EIP, we determined the incidence of ß-lactam drug resistance in Hi that did not produce ßL.

Ninety-three case-isolates of invasive Hi were submitted to us during 2002-3. All case-isolates were susceptible to amoxicillin-clavulanate which contains a ßL inhibitor; 100% were susceptible to ciprofloxacin, cefotaxime, meropenem, and rifampin; 39% were non-susceptible to ampicillin; 9% were non-susceptible to trimethoprim-sulfamethoxazole; 1% were non-susceptible to chloramphenicol; and 1% were non-susceptible to tetracycline. 100% of the ampicillin-resistant case-isolates produced ßL, although one ßL negative case-isolate did exhibit an intermediate ampicillin minimum inhibitory concentration (MIC) of 2 mcg/ml. Five (5%) case-isolates were non-susceptible to >2 antibiotics.

Resistant infections did not appear to differ by serotype, type of infection or case fatality. Ongoing monitoring of susceptibility patterns and ß-lactamase resistance will be useful to detect susceptibility trends in invasive Hi disease. Thanks to our EIP partners (clinicians, laboratories, and infection control professionals), this important public health work continues.


5. HUS Due to Non-O157 Shiga Toxin Producing E. coli
E. coli O157:H7 (O157) is the primary cause of post-diarrheal hemolytic uremic syndrome (HUS). Non-O157 Shiga toxin-producing E. coli (STEC) also can cause HUS; however, this has been documented only occasionally in the U.S., usually as part of outbreak investigations. We attempt to get laboratory confirmation of the etiology for each HUS case reported to us. Stools are cultured for O157 at hospitals or at the MDH. If a case is culture-negative for O157, serology for O157 antibody is conducted by CDC for us, and DNA sweeps from stool culture plates are tested for Shiga toxin genes (stx1 and sxt2) by polymerase chain reaction (PCR) by us. If stx1 or stx2 is detected, stx-positive colonies of E. coli are isolate0 as diabetes are risk factors for developing invd for serotyping by us or CDC.

During 1997-2002, 90 of 92 HUS cases identified in Minnesota had a stool culture for O157; 59 (66%) were culture-positive. An additional 3 (3%) cases were positive for O157 antibody. Five HUS cases due to non-O157 STEC were identified since 2000 (all were negative for O157 by culture and serology). In 2000, a stool culture plate from a 2-year-old female HUS case was positive for stx1 and stx2 by PCR; E. coli O111:nonmotile was subsequently isolated. In 2001, HUS occurred in each of 3 female siblings, ages 10 months, 3 years, and 6 years; the 6-year-old died. Both stx1 and stx2 were detected by PCR of a stool culture plate from the 10-month old; E. coli O111:nonmotile was subsequently isolated. All three siblings were positive for E. coli O111 antibody. In 2002, a fatal HUS case occurred in a 1-year-old female Wisconsin resident who was hospitalized in Minnesota. Stool culture plates obtained from the hospital were negative for stx by PCR. However, stx2 was detected by PCR in a culture of a diaper collected and frozen during the acute diarrheal illness; E. coli O121:H19 was subsequently isolated.

Non-O157 STEC may be an under-recognized cause of HUS in the U.S. Detection of non-O157 STEC infection in HUS cases requires aggressive laboratory testing; PCR for Shiga toxin genes on stool culture plates has been a critical detection tool in Minnesota. Thanks to our EIP partners, the clinicians of these patients, and these patient's families for helping us elucidate these findings.

 

Bug Bytes is a combined effort of the Infectious Disease Epidemiology, Prevention and Control Division and the Public Health Laboratory Division of MDH. We provide Bug Bytes as a way to say THANK YOU to the infection control professionals, laboratorians, local public health professionals, and health care providers who assist us.

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Updated Friday, November 19, 2010 at 02:16PM